An air-equipped turning rod is described of page 56 of the textbook entitled "Technology, Systems, Machines" ("Techniken, Systeme, Machines") by Oskar Frey, Polygraph-Verlag, 1979, in which an external tube receives compressed air over a flexible hose, the tube being formed with air exit holes therethrough. Depending on the width of the web which is to be turned, a second, interior tube can be twisted or longitudinally shifted in order to close off those holes which are not needed to float the web to be turned about the turning bar.
It has been found that all such arrangements cause problems of sealing, that is, have problems in connection with undesired, unintended escape of air from various joints and the like which, frequently, are caused by manufacturing tolerances.